A subset of conotruncal congenital heart disease (CHD) patients studied have been shown to have microdeletions of 22q11.2. The region deleted is large and is likely to code for several contiguous genes. To begin to understand how hemizygosity of this particular chromosomal segment gives rise to the cardiac defects seen, this region must be carefully analyzed and the genes identified. To accomplish this we propose to make a detailed physical map of the region and use this map to isolate overlapping cloned genomic DNA fragments from YACs and cosmids. DNA samples from a selected subset of CHD patients will be used to narrow the critical region. In particular, the breakpoints of patients who represent with smaller deletions will be studied to dissect out the gene(s) within the region likely to be responsible for the conotruncal malformations observed in these patients. Multiple methods will be used to identify and isolate cDNAs from the region. These methods will include mapping of newly isolated chromosome 22-specific genes, directly selecting for cDNAs which map to the critical region using YACs and cosmids and computer analysis of the DNA sequence obtained from large scale sequencing of the critical region. Transcripts identified in this manner will be confirmed and isolated by either hybridization of PCR- based strategies. Thus, important developmentally regulated genes will be identified and characterized. Their role in the pathogenesis of CHD will be examined.